1. Field of the Invention
The present invention relates to polarized wave separators, and more particularly to a polarized wave separator for use in a receiving converter (a low noise blockdown converter, LNB) that receives radio wave from a broadcasting or communication satellite.
2. Description of the Background Art
Microwave being used in satellite broadcasting normally consists of two components. As typical microwave, circularly polarized wave includes clockwise polarized wave and counterclockwise polarized wave. Linearly polarized wave includes vertically polarized wave and horizontally polarized wave.
The receiving converter is required to efficiently separate such two components from each other, and a polarized wave separator is used for such separation of microwave. As a representative of conventional polarized wave separators for use in the receiving converters, a polarized wave separator for separating the components included in circularly polarized wave will now be described.
Referring to FIGS. 24 and 25, a pair of wave receiving probes 104a, 104b is formed on a substrate 103. A waveguide 101 is placed on one side of substrate 103. A waveguide partition wall 101a in a stepped shape is formed within waveguide 101, which partitions the interior of waveguide 101 into two portions.
A wave reflecting unit 102 is placed on the other side of substrate 103. A wave reflecting unit partition wall 102a is formed within wave reflecting unit 102, which partitions the interior thereof into two portions. A wave reflecting surface 102b is formed on an end surface of wave reflecting unit 102 opposite to substrate 103.
On a surface of substrate 103 facing wave reflecting unit 102, an earthed surface (pattern) 105 is formed along end surfaces of wave reflecting unit 102 and its partition wall 102a such that they contact with each other. On the other surface of substrate 103 facing waveguide 101, another earthed surface (not shown) is formed along end surfaces of waveguide 101 and its partition wall 101a such that they contact with each other.
The earthed surface 105 for contact with wave reflecting unit 102 and the earthed surface for contact with waveguide 101 are electrically connected to each other via a through hole 106. Thus, waveguide 101 and wave reflecting unit 102 are both maintained at an earth potential via substrate 103.
The pair of wave receiving probes 104a, 104b is formed on substrate 103 on its side facing wave reflecting unit 102. Interconnection portions of wave receiving probes 104a, 104b are electrically isolated from any of earthed surface 105, wave receiving unit 102 and waveguide 101.
Waveguide partition wall 101a and wave reflecting unit partition wall 102a act to partition the interior of waveguide 101 and wave reflecting unit 102, respectively, into two wave-guiding spaces. Circularly polarized wave caught within waveguide 101 is separated by waveguide partition wall 101a and introduced into respective wave-guiding spaces.
The conventional polarized wave separators have configurations as described above.
With such a conventional polarized wave separator, however, there exist several problems conceivable as follows. To prevent the wave within waveguide 101 and wave reflecting unit 102 from externally escaping, or to reduce noise, it is necessary to ensure that respective end surfaces of partition walls 101a, 102a, waveguide 101 and wave reflecting unit 102 contact their corresponding earthed surfaces.
If the secure contact between wave reflecting unit partition wall 102a and earthed surface 105 on substrate 103 is ensured, however, good contact between the end surface of waveguide 101 and the corresponding earthed surface may not be achieved.
As a result, the wave may escape from waveguide 101, or the wave may not be separated successfully.
In addition, since wave reflecting unit 102 and waveguide 101 are electrically connected to each other via substrate 103, there may arise a problem that the wave introduced into waveguide 101 will be attenuated by substrate 103 before reaching wave reflecting surface 102b, which results in further weakening of the wave. Hereinafter, such reduction in strength of the wave due to escape and/or attenuation will be referred to as xe2x80x9cwave lossxe2x80x9d.
The present invention is directed to solve the conceivable problems as described above. An object of the present invention is to provide a polarized wave separator that ensures separation of radio wave while suppressing escape of the wave, thereby reducing the wave loss.
A polarized wave separator according to the present invention includes a substrate portion, a pair of wave receiving portions, a waveguide, and a wave reflecting unit. The substrate has an opening portion. The pair of wave receiving portions is formed on the substrate on opposite sides in a radial direction of the opening portion. The waveguide is located on one side of the substrate portion, and has a partition wall portion provided therein. The wave reflecting unit is located on the other side of the substrate portion, and has a wave reflecting surface formed on its inner side. The waveguide, substrate portion and wave reflecting unit together form a wave-guiding space. The partition wall portion extends through the opening portion to the wave reflecting unit, and divides the wave reflecting surface into two portions. By the partition wall, the wave-guiding space is partitioned into two spaces, one in which one of the pair of wave receiving portions is located and the other in which the other of the pair of wave receiving portions is located.
According to this polarized wave separator, compared to the case of a conventional polarized wave separator in which the waveguide and the wave reflecting unit are located on respective sides of the substrate portion with no opening therein, the wave-guiding space formed by the waveguide, substrate and wave reflecting unit is partitioned by the single partition wall penetrating the opening formed on the substrate. Therefore, the separated wave caught in the respective wave-guiding spaces is prevented from escaping from one wave-guiding space to the other wave-guiding space both in the waveguide and in the wave reflecting unit near the substrate portion. This improves polarized wave-separating characteristics. In addition, the wave guided in the wave-guiding spaces is propagated to the wave reflecting surface without being interrupted by the substrate portion. This reduces the wave loss. Furthermore, the substrate portion is contacted only by the tubular portion of the wave reflecting unit and the waveguide, so that they both can make good contact with the substrate. Thus, it is possible to prevent the separated wave from escaping outside the waveguide or the tubular portion, so that the wave loss can be reduced.
Preferably, the waveguide is located such that the internal circumference of the waveguide encircles the opening portion. The wave reflecting unit includes the tubular portion that is located on the other side of the substrate portion from the waveguide, and an end surface portion that is located on an end of the tubular portion where a wave reflecting surface is formed. The partition wall portion contacts at least the end surface portion, so that it is electrically connected with the wave reflecting unit.
With such a configuration, conduction between the partition wall portion and the wave reflecting unit is ensured, so that the loss of the separated wave is alleviated. Further, it is possible to prevent escape of the separated wave from one wave-guiding space to the other wave-guiding space at least through a gap between the partition wall portion and the end surface portion, so that the separating characteristics are further improved.
To ensure that the partition wall portion and the wave reflecting unit are electrically connected in a good condition and the wave is prevented from escaping as described above, the following configurations are desirable.
The end portion of the partition portion facing the wave reflecting surface is preferably in a convex shape, and this convex shaped end portion contacts the wave reflecting surface.
Preferably, a groove portion is formed on an inner side of the end surface portion of the wave reflecting unit, so that the end portion of the partition wall portion facing the wave reflecting surface is accepted in the groove portion. In particular, it is desired that the end portion of the partition wall portion is in a saw-tooth waveform or a waveform, and the groove portion is formed in a shape corresponding thereto. This assures the contact between the partition wall portion and the wave reflecting unit.
Still preferably, the end surface portion of the wave reflecting unit is provided with a female screw portion and a male screw portion mounted onto the female screw portion, and the male screw portion contacts the partition wall portion.
Preferably, a slit portion is formed on the end surface portion which penetrates the end surface portion, and the end portion of the partition wall portion facing the wave reflecting surface is inserted into the slit portion.
Still preferably, the end portion of the partition wall portion penetrates the slit portion and is riveted at the outside of the end surface portion.
Preferably, a conductive member is mounted between the end portion of the partition wall portion and the slit portion. The conductive member preferably includes an elastic body or a resin.
Still preferably, the end portion of the partition wall portion penetrates the slit portion and is exposed at the end surface portion, and a conductive member is formed to directly cover the end surface portion and the exposed end portion. The conductive member preferably includes a conductive film, metal foil, conductive paste or conductive adhesive.
Preferably, the end portion of the partition wall portion penetrates the slit portion and is exposed at the end surface portion, and the end surface portion and the exposed end portion are welded.
Still preferably, the partition wall portion contacts the tubular portion, and at the portion where the tubular portion and the partition wall portion contact with each other, a concave portion is provided to either one of the tubular portion and the partition wall portion that is formed along a direction in which the partition wall portion extends, and a convex portion is provided to the other of the tubular portion and the partition wall portion that is fitted into the concave portion.
Preferably, a conductive, earthed cap portion is provided between the partition wall portion and the slit portion to cover the end portion.
In this case, provision of such earthed cap portion ensures that the partition wall portion and the end portion are electrically conducted to each other.
Preferably, the earthed cap portion includes a side portion that is formed towards a direction in which the partition wall portion extends, and a cut and bent portion that is bent towards the slit portion side or towards the partition wall portion side.
In this case, the cut and bent portion further ensures the electrical conduction between the partition wall portion and the end surface portion, and also prevents the earthed cap portion from falling off.
Still preferably, the earthed cap portion includes a hooked portion that closely contacts the wave reflecting surface of the end surface portion.
In this case, by the hooked portion in close contact with the wave reflecting surface, the earthed cap portion is secured on the wave reflecting surface, so that it is reliably mounted in the slit portion.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.